1. Field of the Invention
The present invention relates to an ultra-high-pressure rotary water jet gun for exfoliating rust, scale, concrete coating, burrs, paint film and other materials adhered to or formed on a surface of a metal work or a non-metal work.
2. Description of the Prior Art
In recent years, in various fields of the arts, there is employed a machining apparatus utilizing ultra-high-pressure water, which apparatus projects the ultra-high-pressure water, against the work through its jet nozzle to cut the work or to remove unwanted material present on the surface of the work or wash such material off the surface of the work, under the effect of a high-pressure and high-speed water jet fed with ultra-high-pressure water.
In a conventional type of such machining apparatus utilizing the ultra-high-pressure water, its nozzle is rotated in an orbiting manner so as to broaden its treatment area. Hitherto for example in U.S. Pat. No. 4,448,574, issued to Sachio Shimizu, there is proposed a portable type of apparatus as one of such conventional ultra-high-pressure water jet guns. In this portable type of the ultra-high-pressure water jet gun an electric motor for rotating a water jet nozzle is incorporated in the housing to which a grip is attached. However, since this type of jet gun depends on an electric power source, it has the disadvantage that electric means, including the electric motor, must be protected against water. In case that such electric means is not perfectly protected against water, there is the danger that an electric leak may occur in the apparatus. However, it is expensive to provide a perfect waterproof construction in such electrically operated equipment. In addition to these disadvantages, in the jet gun in which the electric motor is incorporated, there is another disadvantage in that the jet gun is difficult to use due to its heavy weight caused by incorporating the electric motor therein. However, a light-weight electric motor which is employed for improving the ease of use of the jet gun fails to supply sufficient power required by the jet gun, and also, such a light-weight electric motor is apt to burn out due to its overload condition if it is used continuously for a long time. These are disadvantages inherent in the conventional jet gun.